Having expanded west, south and east of Hartford, a 13-year-old Century 21 firm is now looking north.

Hartford-based Century 21 Clemens & Sons Realty has merged with Century 21 Gaetano Realty of South Windsor. The deal means Century 21 Clemens & Sons Realty, founded in 1994 by Curtiss Clemens Sr. and Curtiss Clemens Jr., now has five offices with 170 licensed real estate agents.

“It felt right,” said the elder Clemens, president of the firm. “We closed on the building [July 17], and the response was phenomenal.”

In addition to the new office in South Windsor, the deal added eight agents, he said. In all, the merger took four to six weeks from start to finish, Clemens noted.

Looking to expand into the South Windsor area, his firm previously had approached other realty companies to propose mergers but had been rebuffed, Clemens said.

Then Donna Gaetano called, making her own merger offer.

“We were very pleased that she called us,” Clemens said. “It expands our influence in the market place. Plus it opened a new area for our Commercial Division.”

Century 21 Gaetano Realty was founded in 1962, and Donna Gaetano and her son Dave Gaetano will remain with the firm as vice presidents. Curtiss Clemens Jr., co-owner and executive vice president of the company, will oversee the operations at the South Windsor office.

Century 21 Clemens & Sons Realty started with one office in Hartford and grew with office additions in West Hartford, Rocky Hill, Glastonbury and now South Windsor. The most recent merger prior to the one with Century 21 Gaetano Realty was seven years ago, with The Wallace Co. in West Hartford, according to the elder Clemens. That merger added eight or nine agents, he said.

As for future expansion plans, Clemens added, he has his eye on Farmington Valley.

“If the right opportunity came up, we would take a look at it,” he said. “It has to make sense to us. You have to look around and see what’s out there.”

Another consideration is to make sure a new expansion does not affect the other offices, he said.

“[The offices] are strategically located so that we do not cannibalize our own business,” Clemens noted. In addition to the South Windsor market, the new office will give the company access to other towns, such as Manchester, Vernon and Bolton, he said.

“These are rapidly growing areas,” he said. “We’re always looking to expand our business when it makes sense.”

Even before the expansion into South Windsor, “our offices were reaching east of the [Connecticut] river,” Clemens said. “This just bolsters it and reinforces our efforts.”

Century 21 Real Estate has 73 independently owned offices statewide and 8,300 spread out over 52 countries. The company’s Parsippany, N.J.-based parent, Realogy Corp., also owns the Coldwell Banker, The Corcoran Group, ERA and Sotheby’s International brands, as well as the NRT Inc. subsidiary, which operates the company-owned real estate brokerage offices.

As Century 21 Clemens & Sons Realty was expanding in the brick-and-mortar world, Realogy was expanding in the virtual one.

The company recently launched its OpenHouse.com Web site, which is designed to feature information on thousands of open houses being held by the various Realogy companies. The site allows homebuyers to see schedules for open houses hosted by multiple brokerages in their area of interest; print out a route planner with maps and directions; request more information or schedule a private showing; and sign up for e-mail alerts about future open-house events.

Since the Web site’s switch from a testing phase in the spring, the number of open-house listings posted to the site has jumped from several hundred to more than 20,000 on a typical weekend, according to Realogy. The number of subscribers to its e-mail alert system also has grown, climbing 80 percent in the past two months, according to company figures.